Many different types of devices may be remotely accessible over a network, regardless of physical proximity; however, it may be useful to detect or otherwise ensure physical proximity of a user to the device being accessed. One example of such an application is in a printing device. Detecting physical proximity can be combined with traditional physical access controls (locks, area monitoring, etc.). Thus, for example, a user standing in front of a multi-function device (MFD) may be allowed to scan from the MFD to a mobile device over a network connection, but users who are remotely located may not be permitted to do so. Moreover, some printer functions may require a print job to be released, with the intent being to provide the document to the user upon demand when the user is physically proximal to the printer.
However, such physical proximity detection systems are prone to defeat by a user causing the system to erroneously believe that the user is in physical proximity to the device. For example, if the proof of proximity is static, it may be replayed or reused after an initial access by a physically proximal user. One way this is avoided is by displaying a dynamic access code, which a user must enter on a device to ensure proximity. Another way is to display a two-dimensional glyph or other image, which may be captured by a camera of the remote device. In either case, the captured code/glyph may be forwarded to the server, which responds by determining that the code/glyph is correct and then authorizing the mobile device.
Generally, such codes are displayed on a screen associated with the device; however, some devices lack a screen capable of displaying such codes and, moreover, may not prevent a physically proximal user from relaying the code to a remote user. Furthermore, using a camera of a mobile device may be inconvenient and cumbersome to adequately capture the code, and may require mobile devices with sufficient capabilities to perform, display, and transmit such glyphs or two-dimensional codes. Moreover, some locations may completely prohibit use of cameras, videos, etc., rendering this physical proximity detection technique unusable.